All dogs have the ability to bite, and most will under the circumstances they deem it necessary. Dogs that are put into situations that trigger their sympathetic nervous systems - to fight/flight/or freeze - have the potential to bite. Sometimes freezing or flight is taken away as an option, which further increases the chances a dog will bite. So what this means is basically situations dogs are afraid or someone is attacking them (or it’s perceived that way by the dog), are situations that push dogs to the point they are more likely to bite. 

Each dog is an individual and will have his/her personal feelings about situations that lead to this state. For example, some dogs may fear people approaching and reaching towards them (even if the person is intending it to be a friendly gesture), and others will be excited a person is giving them this attention. 

It’s also possible for trigger stacking to occur - meaning a dog may not bite if one thing bothers him, but if he has several things bother him consecutively it can lead to more of a reaction (fear, frustration, aggression), and the dog could decide to react/bite.

This information is useful, because we can use it to help dogs be more comfortable and live in situations that don’t upset them, or make them feel like they need to bite. Furthermore, positive reinforcement training methods work to help dogs become more comfortable with anything that is a trigger - anything that upsets them. Which ultimately means if a dog has bitten someone, the dog is not inherently bad or defective. It’s just an example of a dog who needs some compassionate help and positive reinforcement/reward training. 

And likewise, this information can be used to evaluate shelter and rescue dogs. Just because some of them may have bitten in the past, does not mean they are not suitable for adoption. It’s our job as people to set dogs up to succeed and be free from fearful and painful situations, to keep them comfortable, happy, and calm by providing for their needs and protecting them from scary situations. When we accomplish this, we can help more dogs find their happy, loving homes, while simultaneously keeping everyone safe.